1. Biotechnology Research Institute, National Research Council Canada, Montreal, Quebec, Canada H4P 2R2, Départment de Génie Physique, Ecole Polytechnique de Montréal, Case, Postale 6079, succ. Centre-ville, Montréal, Quebec, Canada, H3C 3A7, and Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel